The present invention relates to a device for monitoring an elevator area, a method for elevator area monitoring, and a software module for elevator area monitoring.
Elevator systems comprise at least one elevator car which is movable in an elevator shaft or freely along a transport device. The elevator car is usually moved from floor to floor in order to allow persons to board and alight there or in order to be loaded or unloaded there.
The interior space of the elevator car, but also the access region disposed in front of the elevator shaft, is particularly critical since, for example, in the case of faulty functioning of the elevator a risk to persons can arise. As an example, the opening of a shaft door may be mentioned, although no elevator car is located behind the shaft door that is opening. In addition, for example, it is also possible to be caught in the door region.
It is also conceivable that inappropriate behavior of a person, faulty handling of the elevator or inexpert loading or unloading of the elevator leads to problems.
There is therefore noted a tendency to monitor these critical areas in order to be able to recognize problems in good time and, in particular, to avoid risk to persons.
Mechanical, magnetic, inductive or similar switches are frequently used for monitoring the doors of an elevator. In addition, optical systems, such as, for example, light barriers or light gratings are used. With approaches of that kind certain information—for example, about the status of the doors—can be supplied to the elevator control. However, the information content is relatively limited, since, for example, a switch is only in a position of indicating two states (digital information whether a door is open or closed). Monitoring solutions of that kind are predominately limited to the immediate vicinity of the car doors and/or shaft doors.
In order to be able to construct a more complex monitoring system there is needed, for example, a combination of several switches and light barriers.
Optical systems in particular have certain advantages, since by contrast to mechanical solutions they operate contactlessly and are not subject to mechanical wear. Unfortunately, even in the case of more complex optical systems such as are used in elevators the meaningfulness is limited to a few states and the detection range is rather restricted. It is possible to detect, for example, whether anybody is in the door area, and movements are able to be recognized. Larger three-dimensional areas cannot, however, be so reliably monitored. In addition, the reaction time of light barriers or light gratings is approximately 65 milliseconds, which in certain circumstances can be too long.
Certain optical photosensors even enable detection of three-dimensional images, wherein mechanically moved parts—for example, in the form of mirrors—are used. These sensors are complicated and costly.
A system for monitoring elevator doors is shown in PCT Patent Application WO 01/42120, which operates with a pre-programmed processor, a digital camera, an analog camera or a video camera. The camera supplies a sequence of two-dimensional images, through the comparison of which information about the state of elevator doors is made available. This system operates with external light which is intercepted and received by the camera. This leads to problems in situations where the intensity of the outside light strongly varies—for example, in the case of incidence of sunlight—and thus the image brightness strongly increases.
Conversely, the use of such a camera for that purpose can also be problematic when the outside light which is present is insufficient. In the case of area monitoring it is essential that the monitoring functions securely and reliably in all circumstances. A dependence on outside light is problematic from this viewpoint. According to the above-identified PCT patent application there is used a classical pattern recognition approach (pattern matching) in order to be able to evaluate the sequence of two-dimensional images. A system operating according to the PCT patent application with two-dimensional images cannot make any statement about distances. A specific statement about movements and movement directions is possible with such a two-dimensionally operating system only by computer-intensive reprocessing of the supplied images.
A further monitoring system is described in U.S. Pat. No. 5,387,768. The system described there uses a camera, images of which are provided in a complicated mode and manner in order to be able to make a statement about whether and how many persons are present in the region of the elevator. The camera makes recording sequences with different zoom settings so as to be able to produce a statement therefrom about possible movements.
In U.S. Pat. No. 5,345,049 an elevator is described in which it is detected by means of an infrared sensor or infrared sensors whether one or more persons wait in the access area of the elevator. Determination of the number of persons does not take place here.
Three-dimensional semiconductor sensors are known which enable three-dimensional detection of image information. Sensors of that kind are known from, for example, the article “Fast Range Imaging by CMOS Sensor Array Through Multiple Double Short Time Integration (MDSI)”, P. Mengel et al., Siemens AG, Corporate Technology Department, Munich, Germany. Such a three-dimensional semiconductor sensor can be used for three-dimensional monitoring.
A further example is described in the article “A CMOS Photosensor Array for 3D Imaging Using Pulsed Laser”, R. Jeremias et al., 2001 IEEE International Solid-State Circuits Conference, page 252.
Elevator systems with access control exist. Such systems operate, for example, by means of badges and badge reading apparatus. Thus, it is possible to check whether a person is authorized to use the elevator. Only a person recognized by badge can call an elevator and select a destination floor. To that extent systems of that kind function reliably. However, who and how many persons enter the elevator car are hardly capable of checking by current approaches. Access can be additionally controlled by appropriate constructional measures, for example a turnstile, an access gate or other architectonic measures. However, these approaches are complicated and often not suitable for aesthetic reasons.
In the case of present-day identification systems for elevator utilization it thus cannot be ensured that in fact only authorized persons enter an elevator car or leave at a floor for which they have access authorization.